She is a selkie by day, a mermaid by night, she knows this too be true.
Nights were scary before she grew her tail, frightening things grew too large when the sun went down and the stars in the sky didn't light her way. She was a little girl, she was afraid.
One night, when bad things were happening, all of a sudden Maureen looked up at the stars and WHOOOSSSSHHHHH she was swept out of her body. Out of her body into an ocean of stars, star fish, the deep blue sea, she felt her legs fuse together and the movement, back and forth, once terrifying, became her tail swishing, moving through the waves, going deeper and faster, now nobody could catch her! There were starfish in her hair and a seaweed and everything looked blue and green and soft and hazy.
When she awoke the next morning she saw that she had slipped out of her tail and she walked awkwardly on her legs as any selkie does when they come ashore. Things had happened in the night that were not part of her daytime life and it was best left deep down in Neptune's land.
As night approached Maureen could feel her legs prickling. She knew it was time to grow her tail again. She could swim deep and fast and down and down and she never had to be afraid again. No one could catch her under the sea with the scales of her tail glinting in the eyes of the silvery fish around her. She closed her eyes and dove back down and down and down.
The next morning the selkie got dressed and took her little book bag with her, happy to leave her tail, and the night, behind.